From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: Johan Hovold <johan@kernel.org>
Cc: linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 4/5] gnss: ubx: add support for the reset gpio
Date: Tue, 20 Jun 2023 11:41:39 +0200 [thread overview]
Message-ID: <ZJF0U/mIniEksVwZ@ninjato> (raw)
In-Reply-To: <ZJFtdWK5I13YUUcu@hovoldconsulting.com>
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> But can you elaborate on the "disappearing" bit? How exactly does it
> "disappear" when the gnss0 device is *not* opened?
When you send an I2C message with the address of the device, it usually
ACKs it to say "Hi, I am here". When the ublox device is in reset state,
it does not ACK its address. So, tools like "i2cdetect" will not report
the device as "someone is listening there".
Here is the i2cdetect output with the GNSS device open:
# i2cdetect -y -r 15
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: 10 -- -- -- -- -- -- -- -- -- -- -- -- 1d -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- 42 -- -- -- -- -- -- -- -- -- -- -- -- UU
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- 6b -- -- -- --
70: -- UU -- -- UU UU -- --
And with the device closed. Note address 0x42 disappearing:
# i2cdetect -y -r 15
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: 10 -- -- -- -- -- -- -- -- -- -- -- -- 1d -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- UU
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- 6b -- -- -- --
70: -- UU -- -- UU UU -- --
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next prev parent reply other threads:[~2023-06-20 9:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-23 6:43 [RFC PATCH 0/5] gnss: updates to support the Renesas KingFisher board Wolfram Sang
2023-05-23 6:43 ` [RFC PATCH 1/5] WIP: gnss: merge MTK driver into UBX driver Wolfram Sang
2023-06-12 11:35 ` Wolfram Sang
2023-06-20 7:13 ` Johan Hovold
2023-06-20 9:00 ` Wolfram Sang
2023-06-20 10:21 ` Wolfram Sang
2023-06-20 14:50 ` Johan Hovold
2023-05-23 6:43 ` [RFC PATCH 2/5] gnss: ubx: use new helper to remove open coded regulator handling Wolfram Sang
2023-06-20 8:48 ` Johan Hovold
2023-06-20 9:04 ` Wolfram Sang
2023-06-20 9:08 ` Johan Hovold
2023-05-23 6:43 ` [RFC PATCH 3/5] gnss: ubx: 'vcc' can be optional Wolfram Sang
2023-06-20 7:15 ` Johan Hovold
2023-06-20 9:04 ` Wolfram Sang
2023-05-23 6:43 ` [RFC PATCH 4/5] gnss: ubx: add support for the reset gpio Wolfram Sang
2023-06-20 7:17 ` Johan Hovold
2023-06-20 9:06 ` Wolfram Sang
2023-06-20 9:12 ` Johan Hovold
2023-06-20 9:41 ` Wolfram Sang [this message]
2023-06-20 10:05 ` Johan Hovold
2023-06-20 10:14 ` Wolfram Sang
2023-05-23 6:43 ` [RFC PATCH 5/5] arm64: dts: renesas: ulcb-kf: add node for GPS Wolfram Sang
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